If the rose is the undisputed queen of the garden, then crapemyrtles are her knights in shining armor, for when summer temperature rise, and the queen goes into seclusion, that’s when crapemyrtles really begin to shine.
“When sustained daytime temperatures are about 85 degrees F or above, and other species are losing their luster, crapemyrtles begin to produce flower buds for their summer show-off period,” said Carl Whitcomb, PhD. and President of Lacebark, Inc., “Once flowering is triggered to begin, on many cultivars, it continues for 100 to 120 days or more.”
Crapemyrtle, Lagerstroemia indica, is a large flowering shrub or small tree native to China, but it is well adapted to Oklahoma and the southern half of the United States. Through hybridization and selection, crapemyrtle developers expanded the genus to include mid-size and dwarf crapemyrtles for smaller gardens.
“It is such a tough and adaptable plant with the capacity to survive almost any conditions except where the temperature gets below about -5 degrees F., ” said Dr. Whitcomb.
According to Dr. Whitcomb, the common name for L. indica should be written as the compound word, crapemyrtle, and not as crape myrtle, because the plants are not related to the myrtle family. He should know. Dr. Whitcomb, who works and resides in Oklahoma, developed many of the new crapemyrtle varieties in the garden marketplace, including some of the most popular like Tightwad Red® and Dynamite®. L. indica is the plant most often grown in the southern part of the United State and is hardy to USDA Zone 7. L. fauriei, the other form, is hardy as far north as USDA Zone 6.
Not only do crapemyrtles have a long bloom period, they have few pests, and the newer cultivars are very resistant to powdery mildew, a disease that plagued older varieties. As a precaution, plants should always be placed in full sun with good air circulation. Fungicides are rarely needed. I have never sprayed my crapemyrtles for disease. In the late spring and early summer, crapemyrtles can be attacked by the crapemyrtle aphid, Tinocallis kahawaluokalani. Aphid colonies congregate on the underside of leaves. They suck sap out of the leaves and young stems excreting a substance called honeydew. Sooty mold can grow on the honeydew giving new plant growth a dark cast. Ladybugs, also known as ladybird beetles, beneficial wasps and other aphid predators help control these pests. Pesticides are more detrimental to beneficial insects than the aphids so they shouldn’t be used. If a large aphid colony attacks plants, a blast from the hose in the morning should eliminate most aphids and give leaves a chance to dry.
Since crapemyrtles bloom on new wood, Dr. Whitcomb suggests that the old idea of pruning heavily each year should be abandoned.
“Where the severe pruning of crapemyrtles began and why is unknown. the hype has been that you get more flowers. That has not been proven to be true in my research and similar research at the University of Florida.
“Pruning is always stunting because a plant runs on energy and leaves are the manufacturing sites of that energy,” he said, “Anything you do that reduces the number of leaves is stunting compared to a plant that has not been pruned.”
Instead, he suggest planting the right plant for the right place. If you want a dwarf red crapemyrtle, plant one like Tightwad Red® that grows to four feet tall or less. For a taller variety, plant Dynamite® or Red Rocket® that grow to fifteen fee or more. It’s fine to clip oof old flowers and seed capsules, but Dr. Whitcomb is working on creating sterile plants that increase flower producton and reduce the need for pruning.
The Quest for Red
When Dr. Whitcomb left Oklahoma State University in 1985, he selected approximately forty species of plants he believed had promise, but also need improvement. His quest for red flowering crapemyrtles was motivated by a scientific paper he read which concluded that red flowers were highly unlikely due to the lack of proper pigments in crapemyrtle and althea flowers Dr. Whitcomb’s first parent crapemyrtle, from wich all of his plants are descended has medium pink flowers. After generations of selecting and saving seeds from some of the darker pinks he began to see more and more reds. Not only did Dr. Whitcomb select for red flowering plants, he also selected for powdery mildew resistance. He has achieved both and now has several red flowering crapemyrtles, including Dynamite®, Red Rocket®, Siren Red® and the dwarf Tightwad Red®. Each plant has its own distinctive red hue and growth habit.
“The gene pool in L. indica is huge and has lots of variations yet to be revealed. I am pursuing a number of variations, and each year I find fascinating new genetic expression,” said Dr. Whitcomb. He is particularly excited about one of his newest plants, Rhapsody in Pink® that has red-wine foliage and light pink blooms.
“Most crapemyrtle cultivars provide a roller coaster of blooms. The flower show typically begins in late June or early July, then a lull while the seeds mature, then another bloom period and so on,” he said, “With Rhapsody in Pink®, this new sterile cultivar produces a panicle of blooms, then another and another.”
Bustani Plant Farm, Stillwater, Oklahoma;
Bob’s Scott’s Nursery, 10116 West Wilshire Boulevard Yukon, OK 73099;
Sooner Plant Farm, located in Northeastern Oklahoma; and
TLC Nursery, 105 West Memorial Road, Oklahoma City, OK
This article was published in July 2009–I think. It was reprinted with permission from Oklahoma Gardener magazine. In the last few years, many other worthy crapemyrtles have hit the marketplace including miniature and weeping forms. This article highlights my interview with Dr. Whitcomb who is a great resource for our state.